Engines are typically designed according to operating limits associated with certain component attributes. For example, certain engine specifications, such as fuel injection timing, fluid pump design, cooling system capabilities, etc., of an engine may be designed with operating limits corresponding to various parameters, such as engine speed and torque. The relationship between an engine's operating limits and selected operating parameters are sometimes represented as software-based performance maps that an engine controller may access to provide control signals to an engine to ensure the engine operates within the boundaries reflected by the operating limits.
A performance map for a particular engine may include several different performance curves based on varying load conditions. For example, a engine may be designed to follow a first engine calibration performance curve when a transmission is operating in a first set of selected gears and follow a second engine calibration performance curve when the transmission is operating in a second set of gears. Thus, when a vehicle experiences different loads, the controller may provide appropriate control signals to adjust power to the engine. Although such electronic engine control systems allow power to an engine to be adjusted based on varying load conditions, the control is limited to predetermined performance curves and predetermined performance limits. For example, an engine that is associated with a plurality of engine calibration performance curves can only be controlled to “jump” from one curve to another when experiencing a change in load conditions.
One conventional vehicle control system that diverges from the restrictions of known performance curve “jumping” is U.S. Pat. No. 6,173,227 issued to Speicher et al. This patent describes a process for dynamically controlling transmission ratios in a continuously variable gear system. The process determines an upper and lower driving range bounded by, for example, upper and lower transmission gear ratios designed for an engine. Based on conditions exposed, the process allows a host transmission system to be dynamically controlled within a variable range within the upper and lower ratio boundaries. The range may be adjusted by, for example, lowering the upper boundary and/or raising the lower boundary. Although the dynamic control process taught by Speicher et al. allows a system to operate within a variable range, the process is limited to transmission gear ratio applications. Further, Speicher et al. does not allow the upper and/or lower limits to be adjusted beyond their designed limits, thus limiting driving modes to performance ranges that are narrowly defined within these limits.
Additionally, during operations, engines may experience a momentary exposure to a loading condition that may warrant operations that may exceed maximum performance operating limits. One conventional engine control system that attempts to address momentary power demands is described in U.S. Pat. No. 5,123,239 issued to Rodgers. Although the engine control system described by Rodgers enables an engine to receive a momentary “torque burst,” the excess torque provided by the system is limited to starter systems and operations.